Abstract:
Freshwater invertebrates are health indicators for Washington streams. Abundant stoneflies, caddisflies, and mayflies in their aquatic life stage, for instance, indicate that the water is clean and there is food for trout and juvenile salmon.

Since 1993 we have surveyed about 80 wadeable stream sites in Washington state. ... Doing about 20 site visits now per year, we continue to add new sites and are just starting to visit some of our sites for a second time. Through this monitoring we hope to reveal changes in streams that may occur from forest and agricultural practices, urbanization, or other controllable sources of impact.

In addition to sampling for aquatic invertebrates, sites are surveyed for other conditions including canopy cover, stream bed substrate, flow, turbidity, water temperature, acidity (pH), and dissolved oxygen. The criteria for selecting a site are foremost to establish reference conditions for un-surveyed streams or to represent a watershed of interest by the Department of Ecology. Sampling and survey results are stored in a database housed at the Department of Ecology headquarters office near Olympia.

Reference conditions are especially important in developing biologically meaningful criteria to protect resources. The reference condition reflects biological community potential in a stream, and is also used to describe spatial and temporal trends. But to be effective, biological criteria should reflect the variety of natural conditions that occur within a set of similar stream types. This is best achieved through long-term monitoring of reference and degraded sites.

History of the stream biological monitoring in Washington State: Following preliminary surveys in 1993, a consistent strategy for collection of aquatic invertebrates (benthic macroinvertebrates) was developed by 1994 (Ecology Pub #94-113). The monitoring project design focuses on invertebrate community similarity at a regional scale.

Stream dwelling invertebrates respond to changes in the physical or chemical environment. Benthic macroinvertebrates generally inhabit a localized area of a stream throughout their life cycle. Therefore, the individual organisms are continually exposed to any changes that occur in the chemical and physical environment (Rosenberg and Resh 1996). Continuous exposure to the localized condition presents an historical view of a stream's quality.

Washington State can be divided into distinct geographic areas based on topography, climate, land uses, soils, geology, and naturally occurring vegetation. The geographic areas have common names such as the Columbia Plateau, Cascade Range, Eastern Cascades Slopes and Foothills, Coastal Range, Northern Rockies, Puget Lowland, Blue Mountains, or Willamette Valley. Each of the regions have been described using landscape characteristics overlain on each other to locate boundaries (Omernik and Gallant 1986). The resulting boundaries form geographic areas called 'ecoregions'.

In 1993, Ecology initiated a watershed approach to water quality management. Priority basins scheduled for discharge permit issuance are monitored two years in advance. Permit issuance and their timing guide monitoring activities. The five step process used prior to discharger permit approval includes: scoping, monitoring, analysis, planning, and permitting. Scoping refers to identifying the focus for project work within a watershed. Monitoring of waterbodies within the watershed follows with subsequent analysis of the collected information. Planning entails strategies to abate pollution problems in the watershed and this information becomes useful in guiding permitted effluent discharges. This cycle of activities requires five years to complete with monitoring occurring two to three years prior to permit issuance.

Each year, several streams from each of the focus basins are chosen to represent prevailing biological conditions. Sites are selected according to location of the reference condition, and according to the representative dominant land use impacts on stream biotic communities. Where reference conditions within a drainage can not be located, those conditions must be inferred from similar streams within the same ecoregion.

This project uses benthic macroinvertebrates and physical habitat to describe communities under natural conditions and where anthropogenic disturbance is evident. To distinguish natural versus anthropogenic influence, data must be collected at reference sites and at degraded sites over a period of time. Stream invertebrate collections are made during late summer through early fall.

Reference sites are intended to represent one of two reference stream conditions: 1) relatively unimpacted, or 2) least impacted. Relatively unimpacted conditions reflect sites that have experienced very little historical activity that alters stream integrity. Least impacted sites had been degraded historically, but have exhibited some level of recovery. Reference sites are used to describe biological variability due to natural disturbances (i.e., precipitation, drought).

Degraded sites are intended to describe the gradient of human influence on natural stream communities. Identification of what a degraded macroinvertebrate community is and the factor(s) that caused the resulting condition defines severity of impact. This gradient of biological conditions is used to determine the levels of anthropogenic disturbance that are excessive in a waterbody.